1. The Field of the Invention
This invention relates generally to combining computer input devices such as keyboards and touchpads. More specifically, the invention relates to combining the existing components of a keyboard and an integrally constructed touchpad, and for an improved system for coupling a PC board with touchpad circuitry to the keyboard components. The invention also relates to combining a flexible sensor portion of a touchpad, and the rigid circuit component portion of the touchpad, to each other
2. The State of the Art
The prior art includes systems which provide a computer input device having an integrated touchpad. For example, the prior art includes kiosks, computer keyboards, and information appliances that utilize touchpads as an input interface. Probably the most common device is a computer keyboard. It is well known in the art of keyboards and touchpads that they can be included within a same keyboard case or chassis. For example, FIG. 1 shows a top view of a typical QWERTY arranged keyboard 10 from the prior art which has moved the 10-key numeric pad 12 closer to the letter keys, and disposed a touchpad 14 into its place.
FIG. 2 is another keyboard 18 from the prior art which utilizes an ergonomic design. These keyboards 18 have a touchpad 20 disposed beneath the keys in a wrist resting area. This arrangement enables the 10-key keypad 22 to remain in its most familiar location in the keyboard 18.
Unfortunately, disposing a touchpad into a keyboard is not always a straightforward task for some important reasons. For example, it is obviously desirable to make keyboards as inexpensively as possible. While touchpads also have component costs, they also have certain configuration requirements that are different and often more costly than those of keyboards. These aspects will be discussed after explaining the internal structure of a typical prior art keyboard.
FIG. 3 is provided to illustrate one method of manufacturing the internal structure of keyboards. In this figure, the internal layout of the keyboard is shown as being made using several layers of sheets made from a plastic-like material such as mylar. The sheets are generally non-conductive in nature. A first sheet 30 has a plurality of electrical traces 32 laid out using a conductive material such as carbon ink or silver ink. The electrical traces 32 intersect locations that keys make contact with on the first sheet 30 when the keys of a keyboard are depressed. The ink can also be disposed on the mylar using a simple silk screening process.
It is important to understand that this ink application process is not extremely precise, and therefore is generally used in processes where tolerances are high, such as on keyboard electrical traces. The third mylar sheet 36 also has electrical traces 38 which intersect each of the locations of the keys of the keyboard as do the electrical traces 32 of the first sheet 30, but typically in a different axis.
The second or middle mylar sheet 40 is used to separate the first sheet 30 from the third sheet 36 when a key is not being pressed. A plurality of holes 42 are made in the second sheet 40 which also correspond to the locations of keys of the keyboard. Thus, when a key is pressed, an electrical trace 32 on the first sheet 30 is pressed into contact with an electrical trace 38 on the third sheet 36 as made possible because of a corresponding hole 42 in the middle or third sheet 36. This pressing together of a set of electrical traces 32, 38 at a unique location completes an electrical path which is sensed by keyboard circuitry in order to determine which key was pressed. The keyboard circuitry is at least one integrated circuit which is located on a PC board which is separate from the plastic sheets 30, 36, 40.
Having explained typical internal structure and operation of a prior art keyboard, the addition of a touchpad complicates construction because touchpads typically require a rigid PC board as part of the sensing circuitry. For example, a capacitance sensitive touchpad generally requires a PC board to be used as the surface upon which sensing electrodes are disposed. The reason for using the PC board is that the relative positions of the electrodes typically require great precision because prior art touchpad sensing circuitry does not have large manufacturing error tolerances. This intolerance to manufacturing irregularities is generally a function of the touchpad circuitry itself. Touchpad circuitry is inherently sensitive to electrical noise, electrode spacing, and other factors that inhibit the ability to accurately detect and determine the location of a pointing object on the touchpad surface.
For example, X and Y electrical traces are laid out in a very precise pattern or grid. The error tolerance (dynamic range) of all touchpad circuits known to the inventors are such that without a precise grid layout that can only be consistently achieved using a PC board, the touchpads will not function. In other words prior art touchpad are generally so sensitive that it is necessary to include a PC board for the touchpad sensing electrode grids inside the keyboard case if a touchpad is to be included.
In examining the construction of prior art keyboards which include a touchpad, the plastic sheets are typically moved out of the way or minimized in size in order to make room for a PC board that is used for the touchpad sensing electrodes. This is the case with the touchpad shown in FIG. 1. In FIG. 2, the larger size of the ergonomic keyboard allows a PC board to be included without major modifications, but still requires the use of a large PC board for the touchpad. It is also necessary to cut an aperture through the keyboard case to thereby expose the touchpad surface to the pointing object.
In addition to the inclusion of a PC board for the touchpad sensing electrode grids, it is necessary to include some means for connecting the electrical traces 32, 38 on the plastic sheets 30, 36, 40 to control circuitry. The control circuitry is mounted on PC boards inside the keyboard case. This connecter has to be relatively strong because of the nature of the materials being used.
For example, the ink used in the electrical traces can oxidize. Accordingly, a connecter is used which applies a relatively large amount of pressure to force the electrical traces against corresponding electrical traces on a PC board. This pressure typically overcomes the oxidation, but requires the extra hardware involved in making the pressure connection.
It would be an advantage over the prior art to provide a means for reducing the amount of PC board required for a touchpad that is mounted inside a keyboard case. It would be another advantage to improve the connection interface between a PC board and the plastic sheets of the keyboard. It would be another advantage to utilize the plastic sheets for the touchpad sensor electrodes of the touchpad, thereby reducing cost and complexity of the keyboard. Another advantage would be to provide a new way to mount the touchpad sensor electrodes to a keyboard case, regardless of the presence of the plastic sheets for the keyboard itself. Finally, it would be an advantage to provide the touchpad sensor electrodes on a flexible material such as the plastic or mylar sheets, to thereby enable the touchpad to conform to curved surfaces, such as the inside of a keyboard case.
It is an object of the present invention to provide a flexible surface on which the touchpad sensor electrodes are disposed, to thereby enable the surface of the touchpad to be disposed along arcuate surfaces.
It is another object to integrate a touchpad and a keyboard in a keyboard case, wherein the touchpad replaces PC board material normally used for the touchpad sensor electrodes, with the plastic sheets used in construction of the key sensing apparatus.
It is another object to improve the connection between a PC board and plastic sheets used for the touchpad sensing electrodes.
It is another object to eliminate a pressure connector and replace it with a more reliable and less costly connection device.
It is another object to reduce the cost of manufacturing keyboards by manufacturing the touchpad sensor electrodes using the conductive ink used for the electrical traces of the keyboard circuitry.
It is another object to enable the sensor electrodes to be manufactured using a relatively imprecise silk screening process by using touchpad circuitry which has a high degree of tolerance for variations in manufacturing.
It is another object to dispose the sensor electrodes on plastic sheets and then to secure the plastic sheets directly to the underside of a keyboard cover, thereby eliminating the need to cut a hole in the keyboard cover for a user to access the touchpad.
In a preferred embodiment, the present invention is a touchpad formed from the combination of a flexible and non-conductive material used for a touch-sensitive surface, and a PC board on which is mounted the touchpad circuitry, wherein touchpad sensing electrodes are disposed on the touch-sensitive surface by creating electrical traces formed from conductive ink, the touch-sensitive surface being capable of conforming to various arcuate surfaces, and being capable of sensing through a protective housing such that the touch-sensitive surface is protected, and does not come in direct contact with the pointing object.
In a first aspect of the invention, the touchpad is disposed within a keyboard having multiple layers of plastic sheets where electrical traces are disposed thereon using a conductive ink, wherein the touchpad sensor electrodes are disposed on the same plastic sheets, but which are extended into a touchpad area.
In a second aspect of the invention, a new connector couples the electrical traces of the plastic sheets to at least one separate PC board which includes keyboard or touchpad circuitry, so as to generate data regarding keystrokes and touchpad control.
In a third aspect of the invention, touchpad sensing electrodes are disposed on the plastic sheets using a low-cost process which inherently has low manufacturing tolerances such as silk-screening.
In a fourth aspect of the invention, manufacturing tolerances for disposing the touchpad sensing electrodes on the plastic sheets can be low because the circuitry which is driving the touchpad sensing electrodes has a significantly higher dynamic range built-in to its design.
In a fifth aspect of the invention, the touchpad sensing electrode are disposed on plastic sheets which are in turn disposed directly onto the underside of an arcuate top cover of a keyboard case.
In a sixth aspect of the invention, the touchpad circuitry and sensing electrodes are sufficiently sensitive to enable detection and tracking of a pointing object on the keyboard case directly above the touchpad sensing electrodes.
These and other objects, features, advantages and alternative aspects of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description taken in combination with the accompanying drawings.